This disclosure is directed to ball bearings comprising nickel-titanium and to methods of manufacture thereof.
Bearings such as those used in reducing sliding friction (e.g., bushings, journal bearings, sleeve bearings, rifle bearings, plain bearings, or the like) or those used in reducing rolling friction (e.g., ball bearings, roller bearings, or the like) are often manufactured from materials comprising metals, ceramics or organic polymers. Examples of metals are stainless steel, bronze, aluminum, or the like. Examples of ceramics are sapphire, glass, or the like. Examples of polymers are nylon, polyoxymethylene, polytetrafluoroethylene, polyolefins, or the like.
One problem with the aforementioned metals, ceramics and polymers is corrosion. For example bearings manufactured from steel can undergo rusting, which reduces the ability of the bearing to minimize friction over time.
In addition, lubricants used on the bearings also can undergo degradation to reduce the ability of the bearing to minimize friction. Often, the by-products of friction contaminate the lubricants, which render damage to the bearing as well as the lubricant.
It is therefore desirable to manufacture bearings from materials that do not undergo corrosion and that do not produce by-products that damage the bearing or the lubricant. Nitinol 60 (comprising about 60 weight percent nickel and about 40 weight percent titanium) produces parts that are resistant to corrosion. One of the drawbacks of Nitinol 60 is that it is difficult to manufacture components from it that are without casting defects such as voids and pinholes. When a Nitinol 60 component is manufactured by casting a melt into a mold, it generally contains voids and pinholes, which ruins the surface finish and renders the component unusable for its intended application. It is therefore desirable to manufacture Nitinol 60 components that are devoid of casting defects and that can be polished to fine tolerances. Another drawback of Nitinol 60 is that it is very hard and therefore difficult to machine. It is also desirable to manufacture these components to fine tolerances so as to minimize any additional undesirable machining